1. Field of the Invention
This invention relates to a radiation-sensitive resin composition, and more particularly to a radiation-sensitive resin composition especially suitable as a positive resist used for fabricating integrated circuits, that is sensitive to a variety of radiations including ultraviolet radiations, far-ultraviolet radiations, X-radiations and electron radiations.
2. Description of the Prior Art
Positive resists are widely used in the fabrication of integrated circuits. In recent years, as integrated circuits have become more highly integrated, it is sought to provide positive resists that enables highly sensitive formation of high-resolution resist patterns.
With such higher integration, it is also important to coat the resist in a uniform thickness in order to form fine resist patterns in a good dimensional accuracy. Meanwhile, substrates (silicone wafers) show a tendency to increase in diameter from 4 inches to 6 inches and to 8 inches as area per sheet. With an increase in area of the substrate, it commonly becomes difficult to coat the resist in a uniform thickness. Moreover, for economical reasons, it is sought to provide a resist that can be coated not only in a uniform thickness but also in a small coating weight in order to improve efficiency when integrated circuits are fabricated.
In more recent years, pattern defects after development which are a cause of low yield of integrated circuit have come into a great question, which is sought to be solved.
However, any resists that can meet all of these demands are not known in the art. For example, Japanese Pre-examination Patent Publication (kokai) No. 9-160231 discloses a proposal of a resist composition containing a mixed solvent of (a) from 40 to 80% by weight of 3-methoxybutyl acetate and (b) from 60 to 20% by weight of 2-heptanone. Japanese Pre-examination Patent Publication (kokai) No. 9-160228 discloses a proposal of a resist composition containing methyl n-amyl ketone (2-heptanone) in an amount of 70% by weight or more based on the total weight of solvents. The resist compositions in these proposals can be effective for improving coating properties on substrates, but can not be said to have satisfactory performances in respect of sensitivity, resolution and pattern shape.